Benzopyrene induces oxidative stress and increases expression and activities of antioxidant enzymes, and CYP450 and GST metabolizing enzymes in Ulva lactuca (Chlorophyta).

Abstract

Benzopyrene is rapidly incorporated and metabolized, and induces oxidative stress and activation of antioxidant enzymes, and CYP450 and GST metabolizing enzymes in Ulva lactuca. To analyze absorption and metabolism of benzo[a]pyrene (BaP) in Ulva lactuca, the alga was cultivated with 5µM of BaP for 72h. In the culture medium, BaP level rapidly decreased reaching a minimal level at 12h and, in the alga, BaP level increased until 6h, remained stable until 24h, and decreased until 72h indicating that BaP is being metabolized in U. lactuca. In addition, BaP induced an initial increase in hydrogen peroxide decreasing until 24h, superoxide anions level that remained high until 72h, and lipoperoxides that initially increased and decreased until 72h, showing that BaP induced oxidative stress. Activities of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (AP), glutathione reductase (GR) and glutathione peroxidase (GP) were increased, whereas dehydroascorbate reductase (DHAR) activity was unchanged. The level of transcripts encoding these antioxidant enzymes was increased, but transcripts encoding DHAR remained unchanged. Interestingly, the activity of glutathione-S-transferase (GST) was also increased, and inhibitors of cytochrome P450 (CYP450) and GST activities enhanced the level of BaP in algal tissue, suggesting that these enzymes participate in BaP metabolism.